Inspection of pH electrode
1. General inspection methods of glass electrodes
(1) Check the zero potential and set the pH meter to the "mV" measurement range. Insert the glass electrode and the reference electrode into the buffer solution with pH=6.86. The reading of the instrument should be approximately -50~50mV.
(2) Check the slope: Continue with (1), then measure the mV value of the buffer solution with pH=4.00 or pH=9.18, and calculate the slope of the electrode. The relative slope of the electrode should generally be combined with the technical indicators.
Notice:
1) The electrode zero potential value inspection method is only for glass electrodes with an isoelectric point of 7. If the isoelectric point of the glass electrode is not 7, it will be different.
2) For some pH meters, when the calibration and adjustment can meet the requirements and the above inspection results are not outside the range, the electrode can be used.
3) For some smart pH meters, you can directly check the zero potential and slope values obtained from the instrument calibration results.
2. Inspection method of reference electrode
(1) Internal resistance inspection method: Use a laboratory conductivity meter. One end of the electrode socket of the conductivity meter is connected to the reference electrode, and the other end is connected to a metal wire. The reference electrode and the metal wire are immersed in the solution at the same time. The measured internal resistance The resistance should be less than 10kΩ. If the internal resistance is too large, it means that the liquid junction is blocked and should be dealt with.
(2) Electrode potential check: Connect a good reference electrode and the measured reference electrode of the same model to the input ends of the pH meter, then insert KCl solution (or buffer solution with pH=4.00) at the same time, and measure The potential difference should be -3~3mV, and the potential change should be less than ±1mV. Otherwise, the reference electrode should be replaced or regenerated.
(3) Appearance inspection: The silver-silver chloride wire should be dark brown. If it is off-white, it means that the silver chloride has been partially dissolved.
